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Review
. 2022 Jul 26;14(15):3625.
doi: 10.3390/cancers14153625.

Should Peak Dose Be Used to Prescribe Spatially Fractionated Radiation Therapy?-A Review of Preclinical Studies

Cristian Fernandez-Palomo  1 , Sha Chang  2 , Yolanda Prezado  3   4
Affiliations
Review

Should Peak Dose Be Used to Prescribe Spatially Fractionated Radiation Therapy?-A Review of Preclinical Studies

Cristian Fernandez-Palomo et al. Cancers (Basel). .

Abstract

Spatially fractionated radiotherapy (SFRT) is characterized by the coexistence of multiple hot and cold dose subregions throughout the treatment volume. In preclinical studies using single-fraction treatment, SFRT can achieve a significantly higher therapeutic index than conventional radiotherapy (RT). Published clinical studies of SFRT followed by RT have reported promising results for bulky tumors. Several clinical trials are currently underway to further explore the clinical benefits of SFRT. However, we lack the important understanding of the correlation between dosimetric parameters and treatment response that we have in RT. In this work, we reviewed and analyzed this important correlation from previous preclinical SFRT studies. We reviewed studies prior to 2022 that treated animal-bearing tumors with minibeam radiotherapy (MBRT) or microbeam radiotherapy (MRT). Eighteen studies met our selection criteria. Increased lifespan (ILS) relative to control was used as the treatment response. The preclinical SFRT dosimetric parameters analyzed were peak dose, valley dose, average dose, beam width, and beam spacing. We found that valley dose was the dosimetric parameter with the strongest correlation with ILS (p-value < 0.01). For studies using MRT, average dose and peak dose were also significantly correlated with ILS (p-value < 0.05). This first comprehensive review of preclinical SFRT studies shows that the valley dose (rather than the peak dose) correlates best with treatment outcome (ILS).

Keywords: ILS; MBRT; MRT; SFRT; peak dose; valley dose.

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Conflict of interest statement

The authors declare that they have no conflict of interest. The funders had no influence on the design of the study, the collection, analysis, or interpretation of the data, the writing of the manuscript, or the decision to publish the results.

Figures

Figure 1
Figure 1
Illustration of radiation spatial distribution of SFRT. Starting from conventional RT where radiation is seamless, SFRT radiation is spatially fractionated in increasing smaller scales—from clinical GRID-RT (and lattice therapy not shown) to preclinical MBRT to MRT.
Figure 2
Figure 2
Comparative distribution of the data among radiation facilities. No statistical analysis was performed. RStudio was used to create these plots.
Figure 3
Figure 3
Principal component analysis (PCA) of all variables included in this preclinical SFRT study. Dimension or Component 1 (Dim1) accounts for 52.24% of the variance in the data and could represent dose deposition (dosimetry) as valley dose, average dose, peak dose, and PVDR have a positive effect on it. Dimension or Component 2 (Dim2) accounts for 17.85% of the variance in the data and could represent treatment outcome as ILS and valley dose have a positive influence on it.
See this image and copyright information in PMC

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